Fix StackVisitor::GetVReg for reference in shadow frame

Also fixes 457-regs run-test that used to pass an incorrect
vreg kind.

Bug: 25428216
Change-Id: Ic31b51ca0f72350db6325f23087b06e93055d750
diff --git a/runtime/stack.cc b/runtime/stack.cc
index d7edfad..0751f64 100644
--- a/runtime/stack.cc
+++ b/runtime/stack.cc
@@ -265,7 +265,12 @@
     }
   } else {
     DCHECK(cur_shadow_frame_ != nullptr);
-    *val = cur_shadow_frame_->GetVReg(vreg);
+    if (kind == kReferenceVReg) {
+      *val = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(
+          cur_shadow_frame_->GetVRegReference(vreg)));
+    } else {
+      *val = cur_shadow_frame_->GetVReg(vreg);
+    }
     return true;
   }
 }
diff --git a/test/457-regs/regs_jni.cc b/test/457-regs/regs_jni.cc
index 64b2336..79fa8b0 100644
--- a/test/457-regs/regs_jni.cc
+++ b/test/457-regs/regs_jni.cc
@@ -68,7 +68,7 @@
         CHECK(!success);
       }
 
-      CHECK(GetVReg(m, 3, kReferenceVReg, &value));
+      CHECK(GetVReg(m, 3, kIntVReg, &value));
       CHECK_EQ(value, 1u);
 
       CHECK(GetVReg(m, 4, kFloatVReg, &value));